Gear grind after fluid change

this is what I have been reading. The slight grind going into third is much easier to feel since changing the fluid. I would have to really be flying through the gears before with the typical gear oil that was in the transmission. With the shock proof it happens at the easiest of shifts so it totally has something to do with the fluid. The redline mt90 is a thicker viscosity and has less EP additives so in theory it should make a difference. That being said, I could always try and mix a quart of gear oil in the shock proof and see if it improves it before I waste a bunch of money and time swapping fluids completely out...

Exactly.
Transmissions deserve tuning as much as anything else does.
When you drain something you tried out, save and mark what it is.
You may end up going back to one mixture.